Storage management of data streamed from a video source device

ABSTRACT

A computer implemented method for managing data received from a video source device is disclosed. At least a first storage tier and a second storage tier on a storage medium are identified for respectively storing different categories of data. As data streams are received from the video source, the data streams are associated with at least the first storage tier or the second storage tier and data from the received streams are stored in the associated storage tier. When the storage medium is full or meets some other specified maximum capacity threshold, data is deleted beginning with data that has an age that exceeds one or more specified maximum retention times, followed by data with the oldest age from one or both of the first and second storage tiers.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 61/927,923 filed on Jan. 15, 2014, the contents of whichare hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The current disclosure relates generally to managing the storage of datastreamed from a video source device.

BACKGROUND

In a typical video surveillance system, one or more cameras may becommunicatively coupled to a server system. As video data is recorded bythe cameras, it is forwarded to the server system where it is stored forsubsequent retrieval. Client systems are communicatively coupled to theserver system and may be used to request and receive streams of recordedvideo data.

Video surveillance systems are frequently required to be in operationtwenty-four hours a day and seven days a week. As a result, largeamounts of data may be recorded and stored by such systems. There areoften physical limits to the amount of computing memory available forstoring recorded data. The large amount of data that may be recorded insurveillance systems raises the practical issue of how to manage thedata so that the desired data may be quickly accessed, while alsooperating within the storage capacity limits of the system.

SUMMARY

Applicants disclose herein systems and computer implemented methods formanaging data received from a video source device. In an exampleembodiment, a storage management system identifies at least a firststorage area, which may be referred to as a storage tier, for storing afirst category of data and a second storage area or tier for storing asecond category of data. As encoded data streams are received at thestorage management system, the system associates one or more datastreams with the first storage area and associates one or more datastreams with the second storage area. The data streams are stored in theassociated storage areas. The storage management system monitors thestored data to determine whether a storage area and/or the storagemedium is full or meets some other specified maximum capacity threshold.If so, the storage management system deletes data in excess of thethreshold. In an example embodiment, the storage management systemdeletes data having an age that exceeds one or more specified maximumretention times. If the stored data still exceeds a threshold, data withthe oldest age from one or both of the first and second storage tiersmay be deleted.

According to another aspect of the disclosed embodiments, the storagemanagement system may identify a storage ratio specifying the relativeamount of data to be stored in the first and second storage tiers. Whennecessary to maintain the ratio, the data with the oldest age may bedeleted from one or both of the first and second storage tiers such thatthe specified storage ratio is maintained. In an example embodiment, thefirst storage tier may be a long term storage tier having a long termmaximum retention time, and the second storage tier may be a short termstorage tier having a short term maximum retention time that is shorterthan the long term maximum retention time.

According to another aspect of the disclosed embodiments, the datastreams may comprise at least two virtual streams of differentresolutions. The storage management system associates the lowerresolution virtual stream with the short term storage tier, and thehigher resolution virtual stream with the long term storage tier. In anexample scenario, the virtual streams may comprise multiple virtualstreams with each capturing a different region of interest in a field ofview. In such a scenario, the storage management system may associate afirst region of interest with the short term storage area, and a secondregion of interest with a long term storage area. The different regionsof interest may comprise different portions of a field of view, in whichcase, a virtual stream of a central portion of the field of view isassociated with the long term storage tier, and a virtual stream of anon-central portion of the field of view is associated with the shortterm storage tier.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription of Illustrative Embodiments. This Summary is not intended toidentify key features or essential features of the claimed subjectmatter, nor is it intended to be used to limit the scope of the claimedsubject matter. Other features are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary and the following additional description of theillustrative embodiments may be better understood when read inconjunction with the appended drawings. It is understood that potentialembodiments of the disclosed systems and methods are not limited tothose depicted.

FIG. 1 depicts an example surveillance system adapted to generate andstore multiple resolution encodings.

FIG. 2 depicts an example display monitor adapted to display multipleresolution encodings.

FIG. 3 depicts an example video source device and control server adaptedto generate and receive multiple resolution encodings.

FIG. 4 depicts example functional features provided by a video sourcedevice and control server.

FIG. 5 depicts example processing of a video stream comprisingmultiplexed container frames.

FIG. 6 depicts an example video source device response that describesindividual virtual streams comprised in multiple resolution encodings.

FIG. 7 depicts an illustration of an example encoding of a region ofinterest at different resolutions.

FIG. 8 depicts a flow diagram of an example method for streaming datafrom a video source device.

FIG. 9 depicts a flow diagram of an example method for storing datastreams received from a video source device in different locations of adata storage medium.

FIG. 10 depicts a flow diagram of an example method for storing datastreams.

FIG. 11 depicts a diagram of an example process for storing data streamson a data storage medium.

FIG. 12 depicts a flow diagram of an example method for deleting datafrom a data storage medium.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Overview

Generally, digital surveillance systems comprise a number of camerasconnected to a monitoring station. The monitoring station stores videothat is received from the numerous cameras. The monitoring stationallows the received video to be streamed to one or more connectedclients for monitoring. The cameras may be analog or digital camerasconnected to an encoder that streams an encoding of the video at aparticular resolution to the monitoring station. The cameras may furthercomprise IP cameras that include an encoder for streaming an encoding ofthe video at a particular resolution over an IP network to themonitoring station.

The encoders, whether incorporated into a camera or separate from thecamera, may use various possible encoding/compression formats whenencoding the video in order to reduce the required storage size andnetwork bandwidth for streaming the encoded video. Commonly used formatsin the surveillance industry include JPEG, MPEG-2, MPEG-4 and H.264. Amonitoring client will, in some circumstances, display video frommultiple cameras at once. Accordingly, the monitoring client mustreceive and decode multiple video encodings. Even if the video isencoded to reduce the file size, it may be difficult to stream multiplefull resolution streams to a monitoring station over a wide area network(WAN). Compression techniques may further reduce the file size of anencoding without greatly reducing the quality of the encoding for aparticular resolution. However, decoding of such compression techniquesis more computationally complex. Accordingly, a monitoring client maynot be able to decode in a timely manner multiple encodings for display.

In order to provide a plurality of encodings that can be decoded anddisplayed at a monitoring client, it is possible to use heavycompression on the videos to reduce the bandwidth. However, compressiontechniques that allow the multiple video encodings to be decoded anddisplayed in a timely manner at the monitoring client may significantlyreduce the video quality. While the video quality may be sufficient forviewing at the display resolution, it may not provide sufficient qualityto allow detailed viewing of a portion of the encoded video.

In order to provide video that can be streamed in real-time to amonitoring location, as well as video that retains a substantial portionof the video details, the video may be encoded according to variousencoding parameters including, for example, resolution, frame rate, andvarious other quality settings. In an example scenario, a low resolutionencoding may be used to stream the video to monitoring clients, while ahigh resolution encoding may be stored at a central monitoring stationand provided to monitoring locations when a more detailed examination ofa portion of the video is required. However, when viewing the fullresolution encoding it must still be transmitted to the monitoringclient, which may be slow given the large size of the full resolutionencoding.

While some encoding techniques, such as JPEG 2000, can encode multipleresolutions in a single image, it may be desirable to stream multipleindependent encodings from a video source device to a monitoringstation. The multiple independent encodings may be stored for subsequentretrieval. Further, when the encodings are independent, as opposed to asingle encoding as is the case for JPEG 2000, a high resolution encodingcan be deleted from storage when no longer relevant in order to provideadditional storage. The low resolution encoding may be retained forlonger periods of time.

The embodiments described herein relate generally to systems and methodsfor managing the storage of data streams from a video source device on adata storage medium having finite storage capacities. The disclosedstorage management system comprises program code, executable by aprocessor, which determines when a data stream recorded by the camerasshould be stored, and where the data streams should be stored on thedata storage medium. The disclosed system further determines whichpreviously stored data should be deleted when the storage medium isfull, or when other criteria such as, for example, a storage threshold,has been satisfied.

In one particular series of embodiments described herein, a video sourcedevice provides data streams comprising multiple independent resolutionencodings, which may be thought of as collectively forming a “mosaicstream,” to a control server. One of more of the encodings may be avirtual stream recorded at a specified resolution of the entire field ofview of a camera. One or more of the other encodings may comprise amosaic of individually encoded virtual streams of different regions ofinterest. Each different region of interest may be a virtual stream of aparticular area, which may be referred to as a “tile,” in a camera'sfield of view such that a mosaic of tiles can be assembled to representthe entire field of view. For example, a full resolution encoding may beprovided by a 2×2 mosaic of tiles of encoded video. Accordingly, when avideo client wishes to view a detailed view of a portion of the fullframe, only a subset of the mosaic tiles needs to be provided, whichreduces the required bandwidth and processing.

Since each of the different data streams are independently encoded, andcan be independently decoded, the data storage management program may beexecuted to direct different data streams to be stored in differentstorage areas/locations or “tiers” of the storage medium. In someembodiments, the data storage management system may store differenttiles of one of the resolution encodings in different storage tiers. Forexample, the system may identify a storage area or tier as a long termstorage tier and store in that long term storage tier virtual streams oflower resolution encodings of a full frame. The system may designateanother tier as being devoted to short term storage tier and store inthat short term storage tier some or all of the tiles of the fullresolution encoding. In an example embodiment, particularly relevanttiles of the full resolution encoding, such as regions in the frame withmovement, or which capture a door, may be stored in the long termstorage tier, and less relevant tiles may be stored in the short termstorage tier.

The data storage management program may selectively remove certain videodata from the storage medium pursuant to defined criteria. For example,higher resolution encodings may be removed from the short term storagetier before encodings stored on the long term storage tier are removed.The defined criteria for removing or deleting data may comprise anysuitable parameters including, for example, storage capacity limits anda length of time data has been stored.

The systems and methods disclosed herein may be employed for storagemanagement of a mosaic stream comprising multiple independentlydecodable virtual streams wherein a full resolution stream is composedof multiple virtual streams of a region of interest, with each region ofinterest represented by a tile that covers a separate area of the fieldof view of the camera. In such an embodiment, all of the regions ofinterest may be assembled into a grid to represent the entire field ofview.

While some aspects of the disclosed data storage management systems andmethods are described in the context of a mosaic stream, it will beappreciated that the disclosed systems and methods may be used to manageother types of data streams. For example, two cameras (or another typeof video source device) may each send a coordinated H.264 Real-TimeTransport Protocol (RTP) stream, wherein one data stream is a highresolution stream and the other data stream is a low resolution stream.In such an embodiment, the high resolution stream may be stored in theshort term storage tier, and the low resolution stream may be stored inthe long term storage tier. According to another example, a camera maytransmit one JPEG stream serving as a primary video stream. In such anembodiment, one storage medium tier may store even frames of the streamand another storage medium tier may store odd frames of the stream. Inyet another example where one camera sends one H.264 RTP stream, onestorage medium tier is employed to store key frames of the stream andanother storage medium tier is used to store P frames, or predictedpicture frames, of the stream.

Example Encoding and Storage Management System

FIG. 1 depicts an example system for encoding video and storing encodeddata streams. In an example embodiment, the system may be a surveillancesystem capable of providing multiple resolution encodings of video. Thesystem 100 comprises a control server 102 that provides variousfunctionality including receiving video from a plurality of video sourcedevices, managing the storage of the received videos, and streamingvideos to one or more clients. The control server 102 may be provided byone or more physical computers and/or by one or more virtual computers.In one alternative embodiment (not depicted), the control server 102functionality may be implemented by one or more of the video sourcedevices 110, 114 themselves, which can then directly send the multipleencodings to clients. The control server may be connected to a pluralityof digital IP cameras 110 a, 110 b, 110 c, 110 d (referred tocollectively as IP cameras 110) as well as a plurality of streamingencoders 114 a, 114 b (referred to collectively as encoders 114), whichmay be coupled to one or more digital or analog cameras 112 a, 112 b,112 c (referred to collectively as cameras 112). The IP cameras 110 andthe encoders 114 may be referred to collectively as video sourcedevices. The video source devices may stream video to the control serverover a network 116. The network 116 may comprise any suitable technologyand may be provided by one or more individual networks, including wiredlocal area networks (LANs), wireless local area networks (WLAN), as wellas wide area networks (WAN).

The control server 102 provides virtual stream manager functionality. Inan example embodiment, a virtual stream manager resident, which may bereferred to as the “server-device virtual stream manager” or“server-device VS manager,” manages the virtual streams that the controlserver 102 receives from the recording devices. The server-device VSmanager 104 provides functionality for configuring the video sourcedevices 110, 114 in order to stream independent multiple resolutionencodings. The server-device VS manager 104 may also comprisefunctionality to receive streams from video source devices 110, 114 anddemultiplex the received streams into the individual virtual streams.The demultiplexed virtual streams may be combined and re-multiplexed indifferent ways, including, for example, by removing one or more of thevirtual streams. The individual virtual streams of a stream from thevideo source devices 110, 114 may be provided to the storage managementfunctionality 108 for storage.

One or more of the individual virtual streams may be provided toadditional virtual stream manager functionality. For example, thevirtual stream manager, which may be referred to herein as the“server-client virtual stream manager” or “server-client VS manager”106, manages the virtual streams that the control server 102 sends tothe client 142. The individual virtual streams may be provided to theserver-client VS manager 106 either from the storage managementfunctionality 108 or from the server-device VS manager 104. Theserver-client VS manager 106 streams one or more virtual streams to amonitoring client over a network 144.

Each of the video source devices 110, 114 may be configured to providevarious virtual stream encodings depending upon the capabilities of therespective video source devices 110, 114, the capabilities of othercomponents, such as the bandwidth of network 116, the bandwidth ofnetwork 144, the available storage space, and the requirements of thesurveillance system. The video source devices 110, 114 may provide asingle resolution encoding, or a plurality of individual resolutionencodings. Further, each resolution encoding may be provided by a numberof virtual streams. Stream 118 is depicted in FIG. 1 as being streamedfrom IP camera 110 to the control server 102 over network 116.

As depicted, the stream 118 comprises a number of individual resolutionencodings 120, 122, 124. The individual resolution encodings 120, 122,124 are depicted as encoding the same portion of the source video, whichis contemplated as being substantially all of the region of interest ofa sensor of the camera 110 a. Each of the individual resolutionencodings 120, 122, 124 encodes the source video using a respectivecompression algorithm and may reduce the resolution, frame rate and/orvideo quality. For example, the resolution encoding 120 may be encodedto the full resolution of the source, the resolution encoding 122 may beencoded to a half of the source resolution, and the resolution encoding124 may be encoded to a quarter of the source resolution.

Each of the individual resolution encodings 120, 122, 124 may beprovided by one or more virtual streams 126, 128, 130 within the stream118. Each virtual stream 126, 128, 130 comprises at least a portion ofthe video source encoded at the compression level of the respectiveresolution encodings 120, 122, 124. As depicted, the full resolutionencoding 120 is provided by a 3×4 tiling of virtual streams. Each of the12 virtual streams 126 is encoded with the same compression technique,and when the twelve virtual streams are combined they provide the fullresolution of the source video. The resolution encoding 122 is depictedas being provided by a single virtual stream. Accordingly, the virtualstream 128 may have a resolution of ½ of the video source. Similarly,the virtual stream 130 may have a resolution of ¼ of the video source.Although described as providing a tiling of a larger area, the virtualstreams do not need to form tiles; rather, each virtual stream mayencode a particular region of interest, which may comprise the fullsource video, or a portion thereof. The various virtual streams mayoverlap the same region of interest, or encode non-overlapping portionsof the source video.

The server-device VS manager 104 may receive streams such as stream 118from the video source devices 110, 114. The server-device VS manager 104may demultiplex the virtual streams of individual resolution encodings120, 122, 124 from the received stream 118, and the demultiplexedvirtual streams may be passed to the storage management functionality108 for storage and storage management. Additionally, one or more of thevirtual streams may be passed to the server-client VS manager 106 forstreaming to the client.

The storage management functionality 108 comprises a data managementprogram that is executable by a processor in the control server 102 andadapted to manage the storage of the resolution encodings in a datastorage medium 132 as described herein including in connection withFIGS. 10-12. The data management program may pass each or a selectednumber of the resolution encodings 134 to the data storage medium 132.The data management program organizes the stored data by storingdifferent video data in different storage areas which may be referredto, for example, as storage sections or tiers in the data storage medium132. In an example embodiment, the storage tiers may comprise a shortterm storage tier 136, a medium term storage tier 138, and a long termstorage tier 140. A short term storage tier 136 may be used to storeeach of the resolution encodings. The data management program is adaptedto delete video data from each storage tier based on a set of criteria.The data storage medium 132 may be comprised in the same computingsystem as the control server 102. Additionally or alternatively, thedata store 132 may be provided by separate computing devices (notshown). Further still, although depicted as being directly connected tothe control server 102, it is contemplated that the data store 132 maybe coupled to the control server 102 by a network. The data storagemedium 132 may comprise one or more non-volatile computer-readablemediums for persistent data storage such as one or more local harddrives. Alternatively, the persistent storage may be remote hard drivesin cloud storage or in network storage.

As described above, the server-client VS manager 106 may receiveresolution encodings from either the server-device VS manager 104 or thestorage management functionality 108 for streaming to a monitoringclient 142 over network 144. The resolution encodings may be fromdifferent video source devices. As depicted, each resolution encoding146 a, 146 b, 146 c, and 146 d may be streamed individually, or one ormore of resolution encodings may be combined together into a singlestream. In the example scenario depicted in FIG. 1, a number of virtualstreams 148 a, 148 b, 148 c, and 148 d corresponding to the lowresolution encodings from different video source devices are streamed tothe monitoring device 142. The monitoring device 142 may receive anddecode the virtual streams 148 a, 148 b, 148 c, and 148 d and displaythe decoded video 150.

Streaming Multiple Resolution Encodings

FIG. 2 depicts a monitor displaying different resolution encodings ofvideo. FIG. 2 depicts three different views 200, 212, and 218. In anexample embodiment, the monitoring client may initially display view200, which comprises the lowest resolution encodings 202, 204, 206, 208of four virtual streams. For example, the virtual streams from fourdifferent cameras may be displayed simultaneously. One of the lowresolution encodings 202 may be selected for zooming in on, for example,by clicking on it with a mouse or other pointer 210. When the resolutionencoding 202 is displayed full screen, the quality of the encoding maybe lower than desired. Accordingly, the medium resolution encoding 214from the selected camera view can be streamed and displayed as depictedin view 212. A user may wish to zoom in further in order to view aportion 216 of the displayed resolution encoding 214. Again, the qualityof the resolution encoding 214 may not be sufficient when zoomed-in toprovide the desired image quality. Accordingly, the full resolutionencoding may be used in displaying the zoomed in portion 220 as depictedin view 218. As described above, the full resolution encoding maycomprise a number of virtual streams. Accordingly, only the virtualstreams of the full resolution encoding that cover the selected zoomedin region need to be streamed to the monitoring client. For example, ifthe full resolution is provided as a 4×3 grid of virtual streams, thevirtual streams in the top row and the third and fourth columns maycover the desired region.

Providing multiple virtual streams allows efficient bandwidth usage whenstreaming video to a monitoring location regardless of whether videofrom multiple cameras is being displayed, or if only a small portion ofa single camera is zoomed in for display. FIG. 3 depicts a video sourcedevice 316 and functionality as well as a control server 102 andfunctionality capable of streaming multiple resolution encodings. Asshown, the control server 302 comprises a central processing unit 304for processing instructions. Corresponding instructions may be stored inmemory 306. The control server 302 may further comprise non-volatilestorage 308 for persistent storage of data and instructions. The controlserver 302 may still further comprise one or more input/output (I/O)interfaces 310. The I/O interfaces allow input and/or output componentsto be connected to the control server. For example, a network interfacecard (NIC) may be connected to the control server 302 in order toconnect the control server 302 to a communication network. The CPU 304may execute instructions stored in memory. The instructions, depicted as312, when executed may configure the control server 302 to provide theserver-device VS manager 314, along with other functionality describedherein.

The video source device 316, which may be, for example, a camera deviceor system, comprises a central processing unit 318 for processinginstructions. The instructions may be stored in memory 320. The videosource device 316 may further comprise non-volatile storage 322 forpersistent storage of data and instructions. The video source device 316may further comprise one or more input/output (I/O) interfaces 324. TheI/O interfaces allow input and/or output components to be connected tothe video capture. For example, a network interface card (NIC) may beconnected to the input/output interface 324 in order to connect thevideo source device 316 to a communication network. Further, if thevideo source device 316 is a camera, whether IP or analog, the I/Ointerface may further connect a sensor to the CPU for capturing imagedata. The CPU 318 may execute instructions stored in memory. Theinstructions, depicted as 326, when executed may configure the videosource device 316 to provide the device virtual stream (VS) manager 328as well as encoder functionality 330.

The server-device virtual stream (VS) manager 314 of the control server302 and the device VS manager 328 of the video source device 316cooperate in order to configure 332 video source device 316, which mayinclude, for example, a camera, as desired or required. The encoderfunctionality 330 may be configured in order to provide multipleencoding components that can each encode video and specified settings,which may include a number of rows and columns of individually encodedtiles. The encodings provided by the encoding components can be streamedto the control server 302 as depicted by data stream 334.

It will be appreciated that while the Figures and description hereinrefer to video source device 316 and server 102 separately, in someembodiments the functionality from both described systems may exist in asingle system. For example, the video source device 316 may be a camerasystem that provides all of the functionality described herein relatingto cameras and image collection, as well as the functionality describedherein relating to control server 102. In such an embodiment, a camerasystem may operate as a server with the ability to control andcommunicate with other camera systems.

FIG. 4 depicts further video source device functionality and controlserver functionality capable of streaming multiple resolution encodings.The functionality may be provided in, for example, the control server302 described above by instructions stored in the memory. When executedby the CPU of the control server, the instructions may provide networklayer protocol functionality 402, application layer protocolfunctionality 404, and configuration functionality 408. It will beappreciated that other functionality may be provided in the controlserver.

Similarly, video source device functionality may be provided in a videosource device such as the video source device 316 described above byexecuting instructions by a processor. The video source devicefunctionality may include network layer protocol functionality 410,encoder functionality 412, and application layer protocol functionality414. The video source device may provide additional functionality notdepicted in FIG. 4.

The network layer protocol functionality 402, 410 of the control server102 and the video source device 316 cooperate in order to configure thevideo source device in the desired manner. The network layer protocolfunctionality provides a standardized network interface for videodevices and allows for the discovery, configuration, management andcontrol of compliant devices. The network layer protocol functionalityprovides a common interface between the control server 102 and the videosource device 316 that allows the discovery of the video source device316 and its capabilities as well as the configuration of the device. Asdescribed further below, the network layer protocol functionality may beused to configure the encoder functionality 416 in order to set up thedevice to stream multiple independent resolution encodings, includingtiled encodings, as described above. Once configured as desired, thevideo source device may encode source video using the configured encoderfunctionality in order to provide a data stream of the configuredresolution encodings. The data stream from the encoder can betransmitted from the video source device to the control server usingapplication layer protocol functionality 404/414 which provide for realtime control and transport of the data stream 418.

Once the data stream is received at the control server 102, it may beprocessed in order to group virtual streams belonging to the sameresolution encoding together. As described above, a single resolutionencoding may be composed of one or more independently encoded tiles. Theresolution encodings may then be further processed as desired, forexample, for storage or streaming to a monitoring client.

The control server may also comprise configuration functionality 408.The configuration functionality 408 may allow a user to set, view and/ormodify configuration parameters of components of the surveillancesystem. For example, the configuration functionality may allow a desiredencoder configuration for video source devices.

The portion of the video stream 118 shown in FIG. 5 comprises first andsecond container frames 506 a-c (collectively, “container frames 506”)prepared by the video source devices prior to their transmission overthe network 116 to the control server 102. Each of the container frames506 a-c respectively comprises a time stamp 510 a-c common to all thevirtual frames 508 of that container frame 506 a-c. Each of the virtualframe headers comprises a frame delimiter delimiting each of the virtualframes 508 from one another. In the illustrated example embodiment, theframe delimiter comprises the vstream id. The container frames 506 inFIG. 5 each comprises one virtual frame 508 a,c,e for H.264 encodedvideo, and another virtual frame 508 b,d,f for JPEG encoded video. Asopposed to sending the H.264 and JPEG video to the control server overseparate streams each with its own timestamp, in the depictedembodiment, placing the H.264 and JPEG videos into the container frames506 and then transmitting the container frames 506 essentially timedivision multiplexes the H.264 and JPEG videos to the control server102.

Associating a group of virtual frames 508 with a single source frametime stamp facilitates synchronization between virtual frames 508 and,consequently, video from different virtual streams that is displayed onthe client 142. The synchronized virtual streams also result in reducedin latency. When the server-device VS manager 314 receives the stream118, it is able to demultiplex each of the container frames 506 based onthe time stamp 510 of each frame 506, and is subsequently able todemultiplex the container frames 506 from each other and each of thevirtual frames 504 from any other virtual frames 508 within thecontainer frame 506. The control server 302 may subsequently process anyone or more of the container frames 506 and virtual frames 504 asdesired, such as by storing the container frames 506 in the data store132.

FIG. 6 depicts a response from the video source device describingindividual virtual streams that provide the multiple resolutionencodings. The response 600, which may be referred to as descriptioninformation or a description file, describes the stream that will beprovided from the video source device. The response 600 describes eachof the virtual streams in the video stream. The video stream may have anumber of individual virtual streams 610 a, 610 b, 610 c, 612, and 614.The encoding parameters of each virtual stream are provided in theresponse 600. For example, each virtual stream may include a uniqueidentifier 602 of the virtual stream, the area or region of interest 604of the video source encoded by the virtual stream, a resultantresolution 606 of the encoded virtual stream, and an indication of thequality of the encoded virtual stream 608. As depicted schematically,virtual streams may encode different regions of interest at the sameencoder settings. For example, virtual streams 610 a, 610 b, 610 cencode different regions of interest of the source video at the sameencoder settings. Further, virtual streams may encode the same region ofinterest at different parameter settings. For example, virtual streams612 and 614 encode the same region of interest but result in differentresolutions. The description 600 of the stream may be provided invarious formats and provides sufficient information in order to allow acomponent that receives the stream, such as control server, to properlydemultiplex and identify the component virtual streams.

FIG. 7 depicts the encoding of a tile at different resolutions. Avirtual stream may encode a particular area of the video source to aparticular size. For example, the source video may have an area 702 of4944×3280. A first virtual stream may encode a portion 704 of the totalarea located at x=0, y=0, that is the top left of the source video, andhaving dimensions 1232×1080. The first virtual stream may provide a fullresolution encoding of the area 704, which will result in the firstvirtual stream encoding 706 having dimensions 1232×1080. A secondvirtual stream may encode the same area 704, but the encoding may downsample the resolution in order to provide ¼ of the source resolution. Assuch, the second virtual stream 708, which encodes the same source videoarea 704, will have dimensions of 308×270.

FIG. 8 depicts a method 800 of streaming data from a video source device316 to a control sever 302. At block 802, encoding components of a videosource device are configured. The configuring operation may comprisetransmitting one or more configuration commands from, for example,control server 302 to one or more video source devices 316 which maycomprise encoders 114. The encoding components of the video sourcedevice 316 are configured in order to provide a number of virtualstreams within the stream sent from the video source device 316. Theencoding components may be configured in order to provide independentresolution encodings of at least a portion of a source video. At leastone of the independent resolution encodings is provided by a pluralityof virtual streams each of which comprises a tile of a mosaic of theresolution encoding. An encoding component comprised in video sourcedevice 316 may be configured to provide each virtual stream.

Once the encoding components for a stream are configured, at block 804,a description of the stream such as is described above in connectionwith FIG. 6 is communicated from the video source device 316 to thecontrol server 302. In an example embodiment, the stream description maybe provided by the video source device 316 to the control server 302 inresponse to a description request sent by the control server 302. Thereceived description describes the plurality of individual streams thevideo source device is configured to provide. Each of a desiredresolution encoding may be provided by one or more virtual streamsdescribed in the description. The description of each virtual stream mayinclude an identifier of the virtual stream as well as encodinginformation of the virtual stream and an indication of the area of thesource video that is encoded by the virtual stream.

At block 806, the data stream itself is communicated from video sourcedevice 316 and received at control server 302. At block 808, the controlserver 302 associates each virtual stream with a respective resolutionencoding. Identifying which of the virtual streams is associated withthe respective resolution encodings may be done using the information inthe stream description. Additionally, if multiple virtual streams encodethe same area of the source video, it may be necessary to utilizeadditional information encoded in the virtual stream in order todetermine which resolution encoding the virtual stream is associatedwith. Once the respective resolution encoding is associated with eachvirtual stream, the virtual streams of the same resolution encodings maybe further processed. For example, at block 810, the virtual streams ofeach resolution encoding may be provided for storage. The virtualstreams and the stream description 509 may be stored in relation to eachother. Additionally or alternatively, at block 812, one or more of thevirtual streams of a resolution encoding may be streamed to one or moremonitoring clients. It will be appreciated that while in the abovedescription it is implied that a number of virtual streams are processedbefore the individual virtual streams are stored and/or transmitted to aclient, each of the virtual steams is independently decodable and may beimmediately stored and/or sent to a client.

Data Storage Management of Streaming Data

As noted above in connection with FIG. 1, the storage managementfunctionality 108 comprises a data storage management program that isexecutable by a processor in the control server 102. The data storagemanagement program manages the storing of the data stream 118, which maycomprise, for example, video, audio, and metadata, in different areas,sections, or tiers of the data storage medium 132. FIG. 9 depicts amethod performed by the data management storage program to determinewhen a data stream 118 is to be stored, and where certain data in thedata stream is to be stored on the data storage medium 132. Referring toFIG. 9, a processor 901 in the control server 102 executes the datastorage management program to perform a method comprising detecting anyof a series of trigger record events 902 that cause a data stream 118from a device to be recorded whenever an occurrence of a trigger sourceevent 902 is detected. Triggering events may be any information that issuitable for causing streamed data to be recorded. For example, triggerrecord events 902 may include:

1. Scheduled recording 904: Recording of a data stream 118 from a videosource device is triggered based on a user-defined schedule. Schedulesmay be defined for each video source device.

2. Analytics Engine 906: Recording is triggered when a certain analyticcriteria is detected in a field of view of the video source device. Anexample of detectable analytic criteria is motion in a field of view. Ina further example, detecting that analytic criteria has been satisfiedmay comprise determining by analysis of meta data that is associatedwith a video stream whether an event has occurred. For example, the metadata associated with a video stream may indicate various events occurredat particular times during the course of a video stream. In an examplescenario, the meta data may indicate that motion has occurred, or facesor objects have been recognized, at particular times during the video.In an example embodiment, the video stream may have been previouslyanalyzed and the results of the analysis stored in the meta dataassociated with a video stream. In an example scenario, a video streammay have been analyzed at the recording device, e.g., camera, forvarious events such as for motion or the existence of people or objectsand the results of that analysis stored in the meta data.

3. Manual recording 908: Recording is triggered manually by a user. Forexample, recording may be triggered by a human operator through a userinterface device on the client while viewing a live video stream from avideo source device.

4. Rule engine 910: Recording is triggered when one or more user-definedrules are met. Rule inputs may be any event source in the system, suchas, for example, detection of a pan-tilt-zoom (PTZ) command, detectionof an event in a recorded stream such as, for example, the presence of aparticular license plate or human face, or detection of any otherspecified digital input received from another part of the digitalsurveillance system.

In an example embodiment, the data storage management program may employa minimum record time per trigger that determines the pre- andpost-recording buffer configuration. In other words, where the systememploys automated triggering events, the system may store the relevantvideo stream for a prescribed period before the triggering event and fora prescribed period after the triggering event. For example, a defaultvalue of five (5) seconds may be used as a recording buffer. It will beappreciated that the buffer size may be any suitable length and may becustomized by the user.

Separate storage spaces or areas 912 in the data storage media 132,which may be referred to as “bins,” may be allocated to each videosource device. In an example embodiment, each bin 912 may be subdividedinto tiers 914, with each storage area or tier being associated with adifferent category of data. In the example embodiment of FIG. 9, thestorage medium 132 is shown as divided into two bins 912 (Bin A and BinB), one for each of two video storage devices A, B, wherein each bin 912is subdivided into two tiers 914 (tier 0, tier 1). One tier 914 may bedesignated as a long term storage (e.g., Tier 1) and the other tier 914may be designated as short term storage (e.g., Tier 0).

The data storage management program also includes a rules engine fordetermining where each segment of data in the data stream 118 should bestored in the storage medium 132. More particularly, the rules enginemay determine in which of the several storage areas a particular videosegment should be stored. In an example embodiment, the rules engine mayuse metadata that is part of the data stream 118 as input for the rulesengine. In an example scenario, the metadata may include a resolutionand time stamp for each frame of video in the data stream 118. In such ascenario, the rules engine may include a rule that associates a datasegment comprising the virtual stream having the smallest resolutionwith the long term storage tier 914. Other metadata may include theposition of a virtual stream tile in the full resolution frame. Therules engine may employ this metadata to associate virtual streamspositioned in a particular part of the frame (e.g., center) with thelong term storage tier 914. Other metadata may indicate whether avirtual stream has motion recorded therein. The rules engine may employthis metadata to associate virtual streams containing motion with thelong term storage tier 914. In still another example scenario, themetadata may indicate whether a virtual stream is covered by a motionmask. The rules engine may employ this information to associate thecorresponding virtual stream with the long term storage tier 914.

FIG. 10 depicts a method 900 performed by the data management program todetermine whether a data stream 118 should be recorded and, if so,associate data segments in the data stream with a corresponding storagearea or tiers 914 in the storage medium 132. Upon execution by aprocessor in the control server 302, the data management program, atblock 920, monitors inputs for trigger events such as those describedabove. At block 922, when the data management program determines aninput indicates a trigger event 902 has occurred, the program, at block924, analyzes the data stream 118 and inputs metadata into the datastream in the rules engine to associate data segments in the data stream118 with a particular storage area or tier 914. Once the data segmenthas been associated with a particular storage area, at block 926, thedata segment is saved to the associated storage tier 914.

FIG. 11 illustrates processing associated with an example data stream.In the example scenario of FIG. 11, the data stream 118 comprises amosaic stream comprising three independent resolution encodings. Inparticular, in the example illustrated in FIG. 11, the data streamcomprises a full resolution encoding “A,” a medium resolution encoding“B,” and a low resolution encoding “C.” The full resolution encoding Acomprises twelve virtual streams (tile) in a 3×4 grid, wherein each tilerepresents a 1.3 megapixel (MP) portion of the full resolution frame.Each of streams B and C comprise a single virtual stream of a fullregion of interest (ROI) recorded at 2 MP and quarter video graphicsarray (QVGA) resolutions respectively. Once a trigger event 902 has beendetected, the data storage management program uses the metadata in themosaic stream 118 to identify the resolution of each virtual stream (andin the case of the full resolution virtual streams, the position of thatvirtual stream in the full resolution frame). In an example scenario,the program associates the low resolution virtual stream C and the twocentral tiles of the full resolution stream A with a long term storagearea or tier 136. The program associates the medium resolution virtualstream B and each tile of the full resolution virtual stream A exceptfor the two central tiles in the short term storage tier 140.

While FIG. 11 depicts a scenario wherein two tiers 136, 140 areassociated with the virtual streams in the mosaic stream 118 of eachvideo source device, any number of storage areas may be employed. Forexample, three storage tiers 136, 138, 140 may be designated such asshown in FIG. 1, wherein the medium resolution virtual stream B may beassociated with the medium term storage tier 138 (not shown in FIG. 11)instead of with the short term storage tier 138 as described in theabove example. Alternative embodiments may be provided where differentvirtual streams in the mosaic stream 118 may be stored in the short,medium, and long term storage tiers 136, 138, 140. For example, the fullresolution virtual streams may be stored in the long term storage tier,and the lower resolution virtual streams may be stored in the short termstorage tier.

FIG. 12 depicts a process 950 performed by the data storage managementprogram to free up space in the data storage medium 132 when the storagemedium 132 is full or meets some other specified maximum capacitythreshold. Referring to FIG. 12, at block 952, the data storagemanagement program determines whether the data storage medium 132 isfull or has reached some other specified threshold. If not, processingcontinues at block 952 where the data stream is saved in the associatedstorage tier in the manner as discussed above. However, if at block 952the data storage management program determines a threshold for datastored in a particular storage area or areas has been reached orexceeded, at block 954, the program deletes from the storage medium 132any data from any of the video source devices that exceeds a specifiedmaximum retention time. At block 956, the program determines againwhether the storage medium 132 is full or meets some other specifiedmaximum capacity threshold. If not, processing continues at block 952where the data stream is saved in the associated storage tier on thestorage medium 132. If at block 956 the data in the storage area exceedsa threshold, processing continues at block 958 where data is deleted.The data that is deleted may be, for example, the next oldest data inone of the tiers 136, 140 on the storage medium 132.

In an example embodiment, the storage management program may be providedwith a specified storage ratio (“tier ratio”) between the two tiers (orbetween three or more tiers if more than two tiers are specified). Theratio defines the relative amount of data to be stored in each of thetwo or more storage areas. In an embodiment that employs a ratio, atblock 960 of FIG. 12, the data storage management program deletes datafrom the other storage tier 136, 140 in a manner that maintains thespecified ratio. For example, if after deleting all of the data thatexceeds the maximum retention time, the storage threshold continues tobe exceeded, the program may delete the next oldest data which, in anexample scenario, happens to be stored in tier 1. In a scenario wheredeleting data results in the tier ratio becoming unbalanced, the programdeletes some of the oldest data stored in tier 2 until the specifiedtier ratio is re-established.

According to another aspect of the disclosed embodiments, a maximumretention time may be specified for each of the long and short termstorage tiers 136, 140. In an example scenario, the maximum retentiontime of the long term storage tier may be higher than that of the shortterm storage tier. The data storage management program may be configuredto delete any data that is older than the respective maximum retentiontimes of each tier. If all remaining data is younger than the maximumretention times and the storage medium 132 becomes full (or exceeds someother maximum capacity threshold), the data storage management programis configured to delete the oldest content from one of the short andlong term tier storage tiers 136, 140, and to delete the oldest datafrom the other of the short and long term storage tiers 136, 140 untilthe tier ratio is rebalanced.

Accordingly, applicant has disclosed systems and methods for managingthe storage of data streamed from a video source. In a disclosedembodiment, a data stream comprising multiple encoded video streams isreceived. The disclosed system, in response to a triggering event,analyzes the data to determine which of several storage areas or tierseach of the separate encoded video streams should be stored. Each of thestorage areas is designated to store data having particularcharacteristics. The system selects a particular storage area for eachof the encoded video streams based upon the characteristics of the videostreams. The system is adapted to delete data from the storage areas ortiers when predefined thresholds are reached. When a threshold has beenreached, data is selected for deletion using any suitable metricincluding, for example, data that has been stored for the longest lengthof time.

Although the above discloses example methods and system including, amongother components, software executed on hardware, it should be noted thatsuch methods and systems are merely illustrative and should not beconsidered as limiting. For example, it is contemplated that any or allof these hardware and software components could be embodied exclusivelyin hardware, exclusively in software, exclusively in firmware, or in anycombination of hardware, software, and/or firmware. For example, networkserver components could be provided exclusively in the video sourcedevice. In such case, the client would interact directly with thedevice, and the video source device would manage its onboard storage inthis manner. Accordingly, while the following describes example methodsand apparatus, persons having ordinary skills in the art will readilyappreciate that the examples provided are not the only way to implementsuch method and apparatus. For example, the methods may be implementedin one or more pieces of computer hardware, including processors andmicroprocessors, Application Specific Integrated Circuits (ASICs) orother hardware components.

The present disclosure has described various systems and methods withregard to one or more embodiments. However, it will be apparent topersons skilled in the art that a number of variations and modificationscan be made without departing from the teachings of the presentdisclosure. For example, while the Figures and description herein referto camera 118/video source device 316 and control server 102 separately,in some embodiments the functionality from both described systems mayexist in a single system. For example, the video source device 316 maybe a camera system that provides all of the functionality describedherein relating to cameras and image collection, as well as thefunctionality described herein relating to control server 102. In suchan embodiment, a camera system may operate as a server with the abilityto control and communicate with other camera systems.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed:
 1. A computer implemented method for managing data,comprising: a computing system identifying at least a first storage areafor storing a first category of data and a second storage area forstoring a second category of data; the computing system receiving aplurality of data streams data stream composed of a plurality ofresolution encodings that encode at least a portion of a source streamusing at least one different video encoding parameter; the computingsystem associating one or more of the plurality of resolution encodingsdata streams from the received plurality of data streams with the firststorage area and associating one or more of the plurality of resolutionencodings data streams from the received plurality of streams with thesecond storage area; the computing system storing, in the first storagearea, data for the one or more of the plurality of resolution encodingsmore data streams associated with the first storage area and storing, inthe second storage area, data for the one or more of the plurality ofresolution encodings data streams associated with the second storagearea; the computing system determining data stored in at least one ofthe first storage area and the second storage exceeds a threshold; anddeleting data in excess of the threshold, wherein the threshold is basedon either a specified maximum retention time or a specified amount ofdata to be stored in the first storage area and in the second storagearea.
 2. The computer implemented method of claim 1, wherein deletingdata in excess of the threshold comprises deleting data having an agethat exceeds a threshold of one or more specified maximum retentiontimes.
 3. The computer implemented method of claim 1, furthercomprising: identifying a ratio specifying a relative amount of data tobe stored in the first storage area and in the second storage area,wherein deleting data in excess of the threshold comprises deleting datafrom one or both of the first storage area and second storage area suchthat the ratio is maintained.
 4. The computer implemented method ofclaim 3, wherein the first storage area is a long term storage areahaving a long term maximum retention time, and the second storage areais a short term storage area having a short term maximum retention timethat is shorter than the long term maximum retention time.
 5. Thecomputer implemented method of claim 4, wherein receiving the datastream composed of a plurality of resolution encodings comprisesreceiving a first virtual stream capturing a first region of interestand receiving a second virtual stream capturing a second region ofinterest, wherein associating one or more of the plurality of resolutionencodings with the first storage area and associating one or more of theplurality of resolution encodings with the second storage area comprisesassociating the first virtual stream with the first storage area andassociating the second virtual stream with the second storage area. 6.The computer implemented method of claim 5, wherein receiving the firstvirtual stream capturing the first region of interest comprisesreceiving the first virtual stream capturing a first field of view, andwherein receiving the second virtual stream capturing the second regionof interest comprises receiving the second virtual stream capturing asecond field of view, the second field of view being different than thefirst field of view.
 7. The computer implemented method of claim 6,wherein the first field of view comprises a central portion of a largerfield of view, and wherein the second field of view comprises anon-central portion of the larger field of view.
 8. A system formanaging data, comprising: a computing processor; computing memorycommunicatively coupled with the computing processor, the computingmemory having stored therein computer executable instructions that whenexecuted cause the system to perform operations comprising: receiving aplurality of data streams, each composed of a plurality of resolutionencodings that encode at least a portion of a source stream using atleast one different video encoding parameter; identifying a first datastream and a second data stream in the plurality of data streams forrecording; associating the first data stream with a first storage andthe second data stream with a second storage, the first storage and thesecond storage allocated for storing different categories of data;storing data from the first data stream in the first storage; andstoring data from the second data stream in the second storage.
 9. Thesystem of claim 8, wherein identifying the first data stream and thesecond data stream in the plurality of data streams for recordingcomprises detecting a trigger event.
 10. The system of claim 9, whereindetecting the trigger event comprises detecting a user defined scheduleindicating a data stream is to be recorded.
 11. The system of claim 9,wherein detecting the trigger event comprises detecting an analyticcriteria has been satisfied.
 12. The system of claim 11, whereindetecting the analytic criteria has been satisfied comprises determiningby analysis of a video stream that an event has occurred.
 13. The systemof claim 12, wherein determining by analysis of the video stream thatthe event has occurred comprises determining by analysis of the videostream that a motion has taken place in a field of view.
 14. The systemof claim 12, wherein detecting the analytic criteria has been satisfiedcomprises determining by analysis of meta data associated with the videostream that the event has occurred.
 15. The system of claim 14, whereindetermining by analysis of meta data associated with the video streamthat the event has occurred comprises reviewing meta data recordingresults from previous analysis of the video stream.
 16. The system ofclaim 9, wherein detecting the trigger event comprises detecting a userdefined rule has been satisfied.
 17. The system of claim 8, whereinassociating the first data stream with the first storage and the seconddata stream with the second storage, the first storage and the secondstorage allocated for storing different categories of data, comprisesallocating the first data stream to the first storage designated forshort term storage and allocating the second data stream to the secondstorage designated for long term storage.
 18. The system of claim 8,wherein the computing memory has stored therein computer executableinstructions that when executed cause the system to perform furtheroperations comprising: determining a threshold associated with at leastone of the first storage and the second storage has been met; deletingdata from at least one of the first storage and the second storage. 19.A computer implemented method for managing data, comprising: a computingsystem receiving a data stream, the data stream comprising a firstencoding of a source stream, a second encoding of the source stream, anda third encoding of the source stream, each of the first encoding, thesecond encoding, and the third encoding encode at least a portion of thesource stream using at least one different video encoding parameter; thecomputing system detecting a trigger event indicating to record the datastream; the computing system identifying from the data stream the firstencoding, the second encoding, and the third encoding; the computingsystem associating each of the first encoding, the second encoding, andthe third encoding with at least one of at least a first storage and asecond storage, the first storage and the second storage designated forreceiving different categories of data; the computing system detectingdata in either the first storage or the second storage exceeds athreshold; and the computing system identifying data in the firststorage or the second storage for deletion, the identified data beingdata that has been stored in the first storage or the second storage forlonger than a defined retention period.
 20. The computer implementedmethod of claim 19, wherein the first encoding comprises a plurality ofvirtual streams, the second encoding comprises a single virtual stream,and the third encoding comprises a second single virtual stream; andwherein associating each of the first encoding, the second encoding, andthe third encoding with at least one of at least the first storage andthe second storage comprises: associating a subset of the plurality ofvirtual streams comprised in the first encoding with the first storage,and associating the plurality of virtual streams except the subset withthe second storage, associating the virtual stream comprised in thesecond encoding with the second storage, and associating the secondvirtual stream comprised in the third encoding with the third storage.21. The computer implemented method of claim 20, wherein the pluralityof virtual streams comprised in the first encoding comprises a pluralityof virtual streams forming a grid, wherein associating the subset of theplurality of virtual streams with the first storage comprisesassociating with the first storage one or more of the plurality ofvirtual streams that are located centrally in the grid.
 22. The computerimplemented method of claim 21, wherein the first encoding is a highresolution encoding as compared to a resolution of the second encodingand the third encoding, and wherein the second encoding is a lowresolution encoding as compared to the resolution of the first encodingand the third encoding.
 23. The computer implemented method of claim 19,wherein associating each of the first encoding, the second encoding, andthe third encoding with at least one of at least the first storage andthe second storage comprises associating the first encoding with thefirst storage, the second encoding with the second storage, and thethird encoding with the third storage.
 24. The computer implementedmethod of claim 23, wherein associating the first encoding with thefirst storage comprises associating the first encoding with a long termstorage, wherein associating the second encoding in the second storagecomprises associating the second encoding with a medium term storage,and wherein associating the third encoding in the third storagecomprises associating the third encoding with a short term storage. 25.A computer implemented method of managing data, comprising: a computingsystem receiving a data stream, the data stream composed of a pluralityof resolution encodings that encode at least a portion of a source videostream using at least one different video encoding parameter; thecomputing system identifying a first storage for storing the datastream; the computing system determining whether a threshold has beenexceeded in the identified first storage; the computing system, upondetermining the threshold has not been exceeded, storing data associatedwith the received data stream in the first storage; the computingsystem, upon determining the threshold has been exceeded in theidentified first storage, identifying first data for deletion from thefirst storage, deleting the identified first data for deletion,identifying whether the threshold is exceeded after deleting theidentified first data, upon determining the threshold has not beenexceeded after deleting the identified first data, storing dataassociated with the received data stream in the first storage; and upondetermining the threshold is exceeded after deleting the identifiedfirst data, identifying second data for deletion from the first storage.26. The computer implemented method of claim 25, further comprising: thecomputing system determining whether a target ratio of data stored inthe first storage and a second storage is satisfied; the computingsystem, upon determining the target ratio is not satisfied, deletingdata from the second storage sufficient to satisfy the target ratio. 27.The computer implemented method of claim 26, wherein deleting data fromthe second storage sufficient to satisfy the target ratio comprisesdeleting data from the second storage that has been stored in the secondstorage for a longest period of time.
 28. The computer implementedmethod of claim 27, wherein deleting data from the second storage thathas been stored for the longest period of time comprises continuing todelete data that has stored for the longest period of time until thetarget ratio is satisfied.
 29. The computer implemented method of claim27, wherein deleting data from the second storage sufficient to satisfythe target ratio comprises deleting data from the second storage thathas been stored in the second storage for a period that exceeds adefined retention time.
 30. A control system, comprising: a receiveradapted to receive a plurality of container frames collectivelycomprising a single data stream over a network, the single data streamcomposed of a plurality of resolution encodings that encode at least aportion of a source video stream using at least one different videoencoding parameter, each container frame comprising a plurality ofvirtual frames and a container timestamp applicable to each of theplurality of virtual frames, and each of the plurality of virtual framesbeing associated with one of the plurality of resolution encodings; aprocessor adapted to associate each of the received plurality of virtualframes within each container frame with an encoding, identify a storagefor at least one of the received plurality of virtual frames based uponthe encoding associated with the at least one virtual frame, and toreconstruct a virtual stream of the associated virtual frames accordingto the container timestamps; and a transmitter adapted to transmit thevirtual stream over the network.
 31. The control system of claim 30,wherein: each container frame comprises a descriptor describing theplurality of virtual frames; and the processor is further adapted toassociate the descriptor with the virtual stream.
 32. The control systemof claim 31, wherein: the descriptor comprises an indication of an areaof a source video that is encoded.
 33. The control system of claim 32,wherein: the transmitter is further adapted to transmit the virtualstream upon receipt of a request for the virtual stream, the requestcomprising the descriptor.